The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Some embodiments are related in general to equipment for servicing subterranean wells, and in some cases, relate to a cementing head that is intended to drop a combination of darts, balls, bombs or canisters in order to activate downhole equipment, launch cementing plugs, deliver chemical products, or the like.
Tools currently available on the market for downhole services implement a modular design with darts that are preloaded in baskets within the modules. The modules are connected to one another using clamps. The darts are held in place mechanically and released by removing the mechanical obstruction and redirecting the flow of the pumped fluid (hereinafter called “process fluid”) through the dart basket. The darts are then forced through the tool by the fluid. The first dart to be launched is placed in the lowest module, with subsequent darts passing through the baskets vacated by the earlier darts.
Darts in prior art designs are launched by blocking the bypass flow of the process fluid and forcing the fluid through the dart chamber. The dart forms an initial seal when placed into the basket. When fluid enters the dart chamber, pressure builds and breaks the seal, forcing the dart out of the basket, through the tool and into the main process-fluid stream.
Some prior art designs consist of modules such as those described in U.S. Pat. Nos. 4,624,312 and 5,890,537 and UK Patent Application GB 2404210A, incorporated in their entirety by reference thereto. The darts are loaded from the topmost module, through the swivel if necessary, and pushed down to their respective baskets with a long rod. The modules have valves that are used to select between the dart and the bypass flow. The valve itself serves as the mechanical obstruction that prevents the dart from prematurely launching. When the valve is turned, it simultaneously opens a passage for the dart while closing the passage of the bypass flow.
Current valves are manufactured as a single part. Should the valve malfunction or require servicing, the entire cementing head must be returned to a central facility or district for maintenance. Such an occurrence is inconvenient and costly, particularly if the well site is in a remote location, far from the central facility or district. Despite the valuable contributions of the prior art, it therefore remains desirable to provide an improved valve system that can be maintained at the wellsite if necessary.